[project @ 2002-03-28 15:31:05 by simonpj]

Another readHoleResult glitch (fixes rn003)

diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs
index ed0e665..f7a8472 100644 (file)
--- a/ghc/compiler/typecheck/Inst.lhs
+++ b/ghc/compiler/typecheck/Inst.lhs
@@ -41,7 +41,7 @@ import TcHsSyn        ( TcExpr, TcId, TypecheckedHsExpr,
 import TcMonad
 import TcEnv   ( TcIdSet, tcGetInstEnv, tcLookupId )
 import InstEnv ( InstLookupResult(..), lookupInstEnv )
-import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType,
+import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zapToType,
                  zonkTcThetaType, tcInstTyVar, tcInstType,
                )
 import TcType  ( Type, TcType, TcThetaType, TcPredType, TcTauType, TcTyVarSet,
@@ -415,16 +415,19 @@ newOverloadedLit :: InstOrigin
                 -> HsOverLit
                 -> TcType
                 -> NF_TcM (TcExpr, LIE)
-newOverloadedLit orig lit ty
-  | Just expr <- shortCutLit lit ty
+newOverloadedLit orig lit expected_ty
+  | Just expr <- shortCutLit lit expected_ty
   = returnNF_Tc (expr, emptyLIE)
 
   | otherwise
   = tcGetInstLoc orig          `thenNF_Tc` \ loc ->
     tcGetUnique                        `thenNF_Tc` \ new_uniq ->
+    zapToType expected_ty      `thenNF_Tc_` 
+       -- The expected type might be a 'hole' type variable, 
+       -- in which case we must zap it to an ordinary type variable
     let
-       lit_inst = LitInst lit_id lit ty loc
-       lit_id   = mkSysLocal FSLIT("lit") new_uniq ty
+       lit_inst = LitInst lit_id lit expected_ty loc
+       lit_id   = mkSysLocal FSLIT("lit") new_uniq expected_ty
     in
     returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)